Delirium affects up to 50% of hospitalized older adults, and is independently associated with functional and cognitive decline, nursing home placement, mortality, and $164 billion in U.S. healthcare costs. Despite these compelling figures, under-recognition of delirium remains a major problem. In this setting, there is increasing interest in implementing systematic delirium identification in U.S. hospitals, yet, ther is very little evidence on how to implement such programs in an effective and efficient manner. Our goals are to develop a practical, effective, and cost-efficient protocol for detection and monitoring of delirium in high risk hospitalized older adults, and to generate the evidence base needed to facilitate its widespread implementation. The products of our first cycle of funding from R01AG030618, 3D-CAM: Deriving and Validating a 3-minute Diagnostic Assessment for Delirium, will serve as key components of our protocol. These include: 1) the 3D-CAM; a highly performing diagnostic interview for delirium that can be completed in 3 minutes; 2) an ultra-brief (30-40 second) 2-item screener that can effectively rule out delirium. We now propose to 1) validate the screener in 2 independent cohorts; 2) combine the screener and 3D-CAM into a 2-step delirium identification protocol; 3) measure the effectiveness and cost-efficiency of having clinicians administer this protocol; 4) employ qualitative methods to determine barriers and facilitators to implementing the protocol. Thus, our application, READI: Researching Efficient Approaches to Delirium Identification, has the following Specific Aims: Aim 1) To independently validate our 2-item ultra-brief screener in two large, existing cohorts of older patients with rigorously performed delirium assessments: 1) SAGES: Successful Aging after Elective Surgery, a post- surgical sample free of baseline dementia (N=566), and 2) END-DSD: Early Nurse Detection of Delirium Superimposed on Dementia (N=391), an acute hospital sample, all of whom have dementia. Aim 2) In a new cohort of 400 general medicine patients recruited from a large urban academic medical center and a small rural community hospital, to assess the feasibility, administration time, effectiveness, and costs of the 2-step delirium identification protocol performed by physicians and nurses, and the ultra-brief screener performed by certified nursing assistants (CNA's), who will notify the nurse of an abnormal result. Aim 3) To conduct a qualitative study of the delirium identification process in the 400 patients enrolled above, including both direct observation and brief open-ended interviews with participants at the end of each protocol to determine barriers and facilitators to implementation of the protocol. Impact: The current Aims will leverage our previous work, and will give us the necessary tools and knowledge to implement a practical, effective, and cost-efficient protocol for detection and monitoring of delirium in hospitalized older patients. Therefore, our work will move the field of delirium research forward, and has great potential to improve quality of care, reduce costs, and promote the independence of vulnerable older adults.